Derivatives of furan



United States Patent 3,347,872 DERIVATIVES 0F FURAN Anthony J. Passannante, Metuchen, John R. Lovett, Edison, and Perry A. Argabright, Cranford, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Dec. 21, 1960, Ser. No. 77,462 13 Claims. (Cl. 260-3473) This invention relates to a difluoramino (NF adduct of furan which is monosubstituted by a functional group, particularly a functional group that contains carbon linked by a double bond to a hetero atom, such as oxygen or nitrogen and which is reactive with another functional group, such as a hydroxy group, by condensation or addition to form a linkage such as an ester linkage. Furan derivatives containing a high ratio of NF groups linked to carbons in the furan nucleus are good as oxidizer components for high-energy compositions useful as rocket propellants. The functional group in these derivatives makes them valuable reactive intermediates.

The furan nucleus of the compound furan can be remarkably well loaded with NF groups and then be stable as taught in the U.S. Application Ser. No. 77,471, filed by Perry A. Argabright on Dec. 21, 1960, now abandoned.

In accordance with the present invention, the NF loading of a furan derivative having a monofunctional group linked to one carbon in the nucleus is accomplished without adverse effects by or on the functional group.

Functional groups of particular interest in the furan derivatives are those capable of reacting with a hydroxy group to obtain an ester or similar linking of the NF loaded furan to another molecule.

Preferred functional groups are the following:

0 Carbomethoxy -(%O OH;

O Carbonyl halide lCl Isoeyanate N=C=O O Carboxy -il-OH O Carboxaldehyde LH Carbonitrile G N Any of such functional groups (denoted as X) is mono substituted for one hydrogen atom attached to a carbon atom in the ring nucleus of furan, as in the following structural formulae:

l 34: O O

I II III general, suitable conditions for these reactions are: re-

action temperatures in the range of about 100 C. to about 450 C., pressures in the range of 5 to 3000 p.s.i.a., residence times of 0.1 to about 24 hours or less, and about 2 to moles or more of N F per mole of furan derivative. However, a monofunctional group makes the addi- 3,347,872 Patented Get. 17, 1967 tion and even substitution of NF for hydrogen go more easily and completely at temperatures in the range of about to 250 C. and under reduced pressure in the range of about 5 to 14.7 p.s.i.a. to obtain a product in which there is at least 1 NF group attached per carbon atom in the nucleus, or 4 to 6 NF groups (y=4 to 6) as in the following tetrakis NF and generalized formulae:

FZN NFB X X (N 2)v i 5 FZN 0 NM 0 IV V The peculiar ease of preparing the tetrakis NF adducts of monofunctional furans is advantageous for eliminating steps of separating lower NF adducts which have less energy value. Furan, itself, has been found more difiicult to react with N F to the extent that with formation of the tetrakis (NF adduct of furan a substantial amount of bis-adduct is obtained.

Details on the preparation of NF -loaded monofunctional furan derivatives are given in the following eX- amples.

Example 1 .Fur0yl chloride (NF adduct 0.5 cc. (0.69 g.; 0.0053 mole) of furoyl chloride C H O(COCl) was injected into a one-liter glass bulb. This bulb was then cooled and evacuated to remove any air, but no furoyl chloride. The bulb was then enclosed in a heating mantle and attached to a manometer. The total reaction zone volume of the evacuated system was approximately 1100 cc. To this system was charged 2.91 g. (0.028 mole) of N F The reaction mixture of furoyl chloride and N F was heated for 5 hours at C. The N F take-up amounted to approximately 1 g. Distillation of the product yielded 1.5 g. of tetrakis NF adduct (yield: 83% based on furoyl chloride).

Analysis showed that the product contained as much or more NF as needed for the composition Analysis.-Tetrakis NF adduct calculated: N, 16.5%; F, 44.9%; C1, 10.5%. Found: N, 17.2%; F, 45.6%; C1, 10.8%.

The reaction has been found to be quite reproducible at preferred reaction temperatures in the range of 100 C. to 250 C. Adequate purification was accomplished by bulb to bulb distillation. Further identification of the product is based on infrared (I.R.) nuclear magnetic resonance (N.M.R.) and gas chromatography v(G.C.) determinations, all of which indicate that the product contained at least 4 NF;, groups per molecule and a structure consistent with that assigned.

Example 2.-Methyl furoate (NF adduct 0. 63 g. (0.005 mole) of distilled methyl furoate C H O(COOCH was injected into a one-liter bulb. The bulb was then cooled. Air was evacuated from the bulb, which with its contents of methyl furoate was enclosed in a heating mantle and attached to a manometer. To the evacuated bulb system having a total volume of 1100 cc. was charged 0.0216 mole N F The mixture in the bulb was heated for 6 hours at 150 C. The N F take-up was approxi mately 0.8 g. and distillation of the product yielded 0.98 g. of tetrakis NF adduct (yield: 60% based on methyl furoate). Elemental analysis: Presence of more than enough NF in product needed for tetrakis NF adduct of methyl furoa-te having the composition Analysis.Tetrakis adduct calculated: N, 16.8%; F, 45.5%. Found: N, 17.8%; F, 45.5%.

Preferred reaction temperatures for the reaction of methyl furoate with N F are in the range of about 100 C. to 250 C. Repeated tests showed the reaction to be quite reproducible. Characterization of the product based on I.R., G.C., N.M.R. and elemental analysis confirmed the structure.

The described conditions of Examples 1 and 2 were not optimum for obtaining the tetra adducts of other monofunctional furan derivatives. The furyl isocyanate N F reaction product made by heating from 4 to moles N 1 per mole of furyl isocyanate at below 150 C. for from 4 18 hours contained appreciable amounts of unsaturated materials, probably bis isomers. Furfural heated with N F at 100 C. (1 to 5 molar ratio) for 4 hours gave a tar which analyzed for the his (NF- adduct,

However, conditions have been found which allow the preparation of tetrakis (NF adducts and derivatives of higher (N1 contents. The conditions which work for furyl isocyanate are short contact of 1-60 minutes at 250 C. in the presence of large excesses of N F (mole ratios from 4-8 moles of N 1 to 1 of furyl isocyanate). Tetrakis furfural can be prepared, on the other hand, in solution by contacting furfural with N F under pressure for long times 5 hours at room temperature to 150 C. Attempts to add N E; to furfural at subatmospheric pressure in glass resulted, as mentioned, at low temperatures in tar formation. In glass, using the conditions suitable for preparation of the furyl isocyanate tetra adduct (high temperature, short contact), hydrogen replacement in the aldehydic functional group was observed and no tetra furfural adduct was obtained.

Details On the preparation of tetrakis or higher furyl isocyanate and tetrakis furfural follow:

Example 3.Tetrakis (NF furyl isocyanate 0.25 cc. of furyl isocyanate (0.234 g.) was injected into a one-liter glass bulb. This bulb was cooled and evacuated to remove any air but no furyl isocyanate. The bulb was then enclosed in a heating mantle and attached to a manometer. Total volume was the same as in Example 1. To this system was charged 1.25 g. (.012 mole) of N F The reaction mixture of furyl isocyanate and N F was heated quickly (in 20 minutes) to 250 C. and maintained at temperature for minutes. Distillation of the product gave 0.26 g. of tetrakis NF adduct (yield: 40% based on furyl isocyanate).

Analysis showed that the product contained as much or more NF as needed for the composition 150 to 350 C. with short contact times in the range of i 1 to 60 minutes.

Example 4.Pentakis (NF furyl isocyanate 0.224 g. (0.00207 mole) furyl isocyanate was pressured with 282 mm. Hg N F (0.0165 mole). The mixture was heated to 250 C. for minutes, then held 30 minutes at this temperature in a one-liter glass bulb. The cooled product was distilled through a series of traps to yield 0.1 17 g. of product in a wet ice cooled trap and 0.041 g. of adduct in a Dry Ice cooled trap. I.R., G.C. and elemental analysis showed product collected in wet ice trap contained mainly pentakis (NF furyl isocyanate.

Analysis-Found: N, 23.2% (average); F, 51.8%. Theory (tetrakis): N, 22.08%; F, 47.95%. Theory (pentakis): N, 22.75%; F, 51.5%.

The production of pentakis (NF furyl isocyanate, C H O (NF NCO was confirmed.

Example 5.Hexa1kis (N1 fmyl isocyanate 0.249 g. (0.0022 mole) furyl isocyanate was heated with 0.0181 mole N 1 to 250 C. for 20 minutes, then held at this temperature 60 minutes. A yield of 0.069 g. wet ice trap product was obtained. G.C. indicated a high purity major peak area of material having hexakis elemental analysis of composition C HO (NF NCO.

Analysis.-Found: N, 23.4%; F, 52.3%. Theory (hexakis): N, 23.3%; F, 54.2%.

Example 6.Tetrakis furfura'l adduct 0.25 cc. of furfural was dissolved in 2 cc. of CCl contained in a 10 cc. 'steel bomb. N 1 (0.013 mole) 1.35 g. was condensed into the bomb and it was closed. The reaction mixture was then heated at C. during 18 hours. Removal of the N F and solvent left a heavy 1iquid which was distilled to give 0.330 g. of product. This analyzed for a-rnixture of predominantly tetrakis adduct of composition C H O(NF CHO.

Analysis.-'Found: N, 16.72%; F, 45.7%, 47.1%; (1.7%). Theory (tetra): N, 18.4%; F, 50.0%; (1.32%). Theory (bis): N, 14.0%; F, 38.0%; (2.0%). Gas chromatography-2 peaks of approximately equal intensity. I.R.Consistent with mixture of normal his and tetra adducts.

Preferred reaction conditions for furfural with excess N F are superatmospheric pressures, e.g., in the range of about 20 to 3000 p.s.i.g., for contact times of about 1 to 24 hours, and at temperatures in the range of about 20 to 200 C.

The NF adducts of the furan derivatives which contain the reactive functional groups, as a class, are fairly good NF oxidizers in that they contain at least 4 NF groups per 5 to 6 carbon atoms in the molecule, but they have even more significant value as intermediate reactants in making polymer binders and other compounds of increased energy values.

A polymer, such as polyvinyl alcohol, contains a number (11) of recurring units bearing a hydroxy group characterized as follows:

By reacting polyvinyl alcohol with an NF adduct of furoyl chloride, of methyl furoate, or of furyl isocyanate, such adduct containing the number (y) of NF groups, the following kinds of modified polymers are obtained:

Modified polymers of the above Types V and VI have been synthesized. In these the multi NF loaded furan is linked by an ester group (carboxylic or carbamic) to the hydrocarbon chain of the polymer which may contain 10 to 10,000 or more recurring units. In the units shown, for y=4 to 6, the unit contains 4 to 6 NF groups for 7 carbon atoms.

Lower molecular weight compounds containing a hydroxy group also react with the NF loaded furan derivatives, e.g. trinitroethanol, to obtain a mixed polynitrodifluoramino oxidizer.

A technique for reacting the NF -furan derivatives with polyvinyl alcohol is described and claimed in US. application Ser. No. 77,463 (IN-48) of A. I. Passannante filed Dec. 21, 1960. This method involves use of a liquid organic diluent, e.g. nitrobenzene, acetonitrile, or tetrahydrofuran which solvates polyvinyl alcohol, and reacting the polymer thus solvated with excess proportion of the isocyanate adduct at about 20 to 100 C. The resulting modified polymer (V or VI) then can be used in proportions of up to 30 wt. percent as binder with liquid NF oxidizer (tetrakis NF butane), oxygen oxidizer (hexanitroethane) and powdered boron to make up solid composites having specific impulses ratings of 270 to 290. A procedure for reaction with lower molecular weight alcohols, e.g. trinitroethanol as shown and claimed in US. application Ser. No. 77,464 (Case IN-62) of A. I. Passannante, filed Dec. 21, 1960, involves reaction of the alcohol in excess with the NF adduct of the compound having a functional group, e.g. isocyanate at to 50 C. and recovery of product by precipitation from solution. US. application Ser. No. 77,465 of I. R. Michael et al., filed Dec. 21, 1960, is concerned with NF adducts of bifunctional furan derivatives which, in general, are made by reaction of bifunctional furan derivatives with N F under superatmospheric pressure with the aid of a solvent.

What is claimed is: 1. NF adduct of furan containing a functional substituent as in the formula:

wherein X is a monofunction al group of the class consisting of carbomethoxy, carbonyl halide, isocyanate, carboxy, carboxaldehyde and carbonitrile linked to a carbon atom in the furan nucleus and y indicating the number 4 to 6 of NE; groups linked to carbon atoms in said nucleus.

. Tetrakis (NF furoyl chloride.

. Tetrakis (NF methyl furoate.

. Tetrakis (NF furyl isocyanate.

. Tetrakis (NF furfural.

. Pentakis (NF furyl isocyanate.

. Hexakis (NF furyl isocyanate.

. Tetrakis (NF adduct of furoic acid.

Process for preparing a turn derivative having an NF group attached to each carbon atom of a furan nucleus and having a single functional substituent group attached to a carbon atom in the furan nucleus, which comprises reacting furan monosubstituted by a single functional group attached to a carbon atom in the funan nucleus with excess N F at a reaction temperature in the range of about to 400 C., said functional group being selected from the class consisting of carbomethoxy, carbonyl halide, isocyanate, carboxy, carboxaldehyde, and carbonitrile functional groups, and recovering resulting tetrakis (NF adduct of the furan having the functional group substituent.

10. Process as in claim 9, in which the substituted furan reacted With N F is furyl isocyanate and the reaction temperature is in the range of to 350 C. to obtain from 4 to 6 NF groups attached to the carbon atoms of the furan nucleus.

11. Process as in claim 9, in which the substituted furan reacted with N F is methyl furoate and the reaction temperature is in the range of 100 to 250 C.

12. Process as in claim 9, in which the substituted furan reacted with N F is fur oyl chloride and the reaction temperature is in the range of 100 to 250 C.

13. Method for preparing tetrakis (NF furfural which comprises, reacting furfural with excess N F under superatmospheric pressure at a temperature in the range of about 20 to 200 C. for a period to form tetrakis (NF furfural as product and recovering said product.

References Cited Hoffman et a1., Chemical Reviews, vol. 62 pages 1-18 (1962).

Banks, Fluorocarbons and Their Derivatives, pages 82 to 91 (1964).

NICHOLAS S. RIZZIO, Primary Examiner.

L. D. ROSDOL, Examiner.

I. W. WHISLER, Assistant Examiner. 

1. NF2 ADDUCT OF FURAN CONTAINING A FUNCTIONAL SUBSTITUENT AS IN THE FORMULA: 